User input on subsequent images to store coordinates - image

Question

function main()
clear all;clc;
path='.\image_files\'; %___________image files path
path_posmap='.\pos_maps\';%_________stores positions of agents
NumOfImages = length(dir(path)) - 2;
w = dir(path);
img_names={}; %________stores names of all images
for i=3:NumOfImages+2,
img_names{i-2} = w(i).name;
end
for i=1:numel(img_names),
imname = [ path img_names{i}];
im0 = imread(imname);
imageHandle =imshow(im0);%_____________displays the image
xlabel(num2str(i));
set(imageHandle,'ButtonDownFcn',#ImageClickCallback);
end
end
function coordinates=ImageClickCallback ( objectHandle , eventData )
axesHandle = get(objectHandle,'Parent');
coordinates = get(axesHandle,'CurrentPoint');
coordinates = coordinates(1,1:2);
message = sprintf('x: %.1f , y: %.1f',coordinates (1) ,coordinates (2));
disp(coordinates); %___ add these coordinates for each image
close(gcf);
end
I want to display a series of images to a user. For each image request input from the user in the form of a mouse click on the image. Store the coordinates of each click in a matrix. Thus, in end having a matrix of dimension num_images x 2.
But in the above
a. I can't get the coordinates returned from the function ImageClickCallback
b. I am unable to close the image and display a new one whenever the user clicks.

Answer 1

I have no MATLAB here right now, so there are a couple guesses in my answer. Here we go:
Closing Figures
You don't close the image, so it won't close. Just add close gcf; at the end of your callback.
Passing Data
Now to get the coordinates I'd suggest using the base workspace instead of a global variable, or pass an argument to your callback.
Means I'd use assignin('base','newcords',coordinates); at the end of your callback.
Use evalin to get your coordinates back from the base workspace. You can try to access newcords without evalin, however I am pretty sure it isn't going to work.
newcords=evalin('base','newcords');
Now you create a new Variable (initialize it outside the for-loop), which holds all coordinates, assuming 2D-coordinates: allcords=zeros(2,numel(img_name));
Write the coordinates from the callback into your new-allcords-variable.
allcords(1,i)=newcords(1);
allcords(2,i)=newcords(2);
On Second thought you don't need to pass the coordinates back from the callback, go with:
Initialize allcords outside your loop:
allcords=zeros(2,1);
In your callback:
allcords=evalin('base',allcords);
allcordssize=size(allcords):
if min(allcordssize)=1
allcords(1,end)=coordinates(1);
allcords(2,end)=coordinates(2);
assignin('base','allcords',allcords);
else
allcords(1,end+1)=coordinates(1);
allcords(2,end+1)=coordinates(2);
assignin('base','allcords',allcords);
end
close gcf %close picture
With that you have all your coordinates from your callback. Another way you could use is, as I mentioned above, passing a variable to your callback.
Make sure data is matched with correct figure
The second problem is, your for loop does open all pictures at once I guess? (I Have no MATLAB available). So how about using uiwait(gcf); in your for loop? (After your set). This way you know which coordinates are assigned to which figure (also if all pictures are opened your coordinates are reverse to the img-list-indexes).
P.S.: I'm not sure if uiwait works in this case, what would work for sure is if you create a single GUI with just 1 handle (for your image), and instead of closing your figure just redraw your image each time your coordinates are chosen. Or load your GUI each loop-iteration, and pass the image name to the GUI.